The invention is well suited for a nozzle which is used in the treatment of a web that is composed of any suitable material, e.g. metal, textile, pulp, or paper. One such nozzle, described in U.S. Pat. No. 4,021,931, has a relatively long tapering chamber in which fluid is circulated. The nozzle is provided with a number of orifices through which fluid flows from the chamber for impingement against an adjacent traveling web. This particular nozzle is unique in that it provides a deflector tab which is attached to the upstream side of each orifice and extends into the chamber in an upstream direction. This tab arrangement has been found to be effective in eliminating the velocity vector or component resulting from dynamic fluid pressure at the orifice, thereby leaving only the velocity vector resulting from static fluid pressure at the orifice. The elimination of this vector causes fluid to flow from the orifice in a direction such that the fluid impinges against an adjacent traveling web in a direction normal to the plane of the web, such impingement being the most preferred and beneficial, but difficult to achieve. One of the problems of this particular tab arrangement, however, is that lint or other such materials carried by the hot air used, for example, in the drying of the web, becomes caught on the upstream side of the tab and eventually builds-up to partially block the chamber and orifice and reduce the effectiveness of the nozzle. The invention is directed to an improved orifice which is oriented to prevent the accumulation of such material and produce a desired directional impingement of fluid against an adjacent web.
Briefly stated, the invention is in a nozzle for impinging fluid against a traveling web. The nozzle comprises a fluid emitting wall which at least partially encloses a chamber in which fluid is circulated, under pressure, and a plurality of orifices which are disposed in the wall in communication with the chamber and through which fluid passes from the chamber. The nozzle is characterized by means for direction fluid from the plurality of orifices in a desired direction including means for positioning the orifices so that the resultant vector of vectors representing fluid velocities due to static and dynamic pressures at the orifices, is in the desired direction.
The foregoing invention can be achieved by an orifice that comprises a dimple-shaped cavity that can be equally divided into two portions, an upstream portion and a downstream portion, relative to the flow of fluid in the chamber past a dividing line of the cavity between the portions. The orifice further comprises an opening in the downstream portion of the cavity when the cavity extends into the chamber. Similar results can be achieved when the opening is placed in the upstream portion of a cavity which extends outwardly of the chamber. In both cases, the opening is in tilted relation such that the resultant velocity vector, as indicated above, is in the desired direction of flow which is preferable normal to the plane of a web which travels adjacent the nozzle.
The invention can also be achieved by utilizing a conventional orifice in combination with a tab which is attached to the upstream side of the orifice and extends into the chamber in a downstream direction to form between the free end of the tab and the downstream side of the orifice, a restricted opening, the plane of which is similarly tilted so that the resultant velocity vector is in the desired direction of flow which is preferably normal to the plane of the traveling web.
It can be appreciated that the inventive concept can be utilized to determine and produce any desired directional flow or impingement of fluid against a traveling web which, in the past, has largely been accomplished by trial and error experimentation.